DTC P0123 Throttle Position (TP)Sensor Circuit High Voltage. Chevrolet PJJ 2000

For 1990-2009 cars
Engine Controls Components
Engine Data Sensors
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice

### Circuit Description

The PCM supplies a 5.0 V reference signal and a ground to the sensor. The TP sensor sends a voltage signal back to the PCM relative to the throttle plate opening. The voltage will vary from approximately 0.35 V at closed throttle, to over 4.65 V at wide open throttle.

### Conditions for Running the DTC

• | DTCs P0107 or P0108 not set.

• | Engine is running.

• | MAP is less than 60 kPa.

• | Engine speed is less than 1500 RPM.

| Or

• | DTCs P0107 or P0108 not set.

• | Engine is running.

• | MAP is more than 60 kPa.

• | Engine speed is more than 1500 RPM.

### Conditions for Setting the DTC

The TP sensor voltage is more than 3.9 volts for 15 seconds when the engine speed is less than 1500 RPM.

Or

TP sensor voltage is more than 4.8 volts when the engine speed is more than 1500 RPM for 15 seconds.

### Action Taken When the DTC Sets

• | The Malfunction Indicator Lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with the fault active.

• | The PCM will record the operating conditions at the time that the diagnostic fails. This information will store in the Freeze Frame and Failure Records buffers.

• | A history DTC stores.

• | The coolant fan turns ON.

• | The TP angle will default to 0 percent when the vehicle speed is less than 3 km/h (2 mph) and 10 percent when the vehicle speed is greater than 3 km/h (2 mph) (The scan tool will display the defaulted value).

### Conditions for Clearing the MIL/DTC

• | The MIL will turn OFF after three consecutive ignition cycles in which the diagnostic runs without a fault.

• | A history DTC will clear after 40 consecutive warm up cycles without a fault.

• | Use a scan tool to clear the DTCs.

### Diagnostic Aids

If a DTC P0123 cannot be duplicated, the information included in the Freeze Frame data can be useful. Use the scan tool DTC information data to determine the status of the DTC. If the DTC occurs intermittently, use the DTC P0105 Diagnostic table in order to help isolate the problem.

With the ignition ON and the throttle at closed position, the voltage should read between 0.20V and 0.90V and increase steadily to over 4.5V at wide open throttle.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. With the throttle closed, the TP sensor voltage should read less than 0.80 volts. If the TP sensor voltage does not read less than 0.80 volts, check for a binding or a sticking throttle cable.

2. The PCM and the wiring are OK if the TP sensor voltage is less than 0.3 volts with the TP sensor electrical connector disconnected.

3. Probing the ground circuit with a test lamp checks the circuit for high resistance which will cause a DTC P0123 to set.

4. Important: The Powertrain Control Module (PCM) uses a single internal 5.0 volt power supply to supply power to all the engine control components. If one component shorts its 5.0 volt reference circuit to ground or battery voltage, the other 5.0 volt reference circuits will also have a low or high voltage.

   A shorted 5.0 volt reference circuit will also set additional DTCs.

5. Reprogram the replacement PCM and perform the Crankshaft Position System Variation Learn procedure.

#### DTC P0123-Throttle Position (TP) Sensor Circuit-High Voltage

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check

2

1. Turn ON the ignition, with the engine OFF.
2. Verify that the throttle is closed.
3. Install a scan tool.

Does the TP sensor voltage measure greater than the specified value?

0.8 V

Go to Step 4

Go to Step 3

3

1. Review the Freeze Frame data and record the parameters.
2. Start the engine.
3. Operate the vehicle within the Freeze Frame conditions and Conditions for Running the DTC as specified.

Does the TP sensor voltage measure greater than the specified value?

3.9 V

Go to Step 4

Go to Diagnostic Aids

4

1. Turn OFF the ignition.
2. Disconnect the TP sensor connector.
3. Turn ON the ignition, with the engine OFF.

Does the TP sensor voltage measure less than the specified value?

0.3 V

Go to Step 5

Go to Step 6

5

1. Connect a test lamp to B+.
2. Probe the TP sensor ground circuit terminal at the TP sensor harness connector.

Does the test lamp illuminate?

--

Go to Step 7

Go to Step 9

6

1. Turn OFF the ignition.
2. Test the TP sensor signal circuit for a short to voltage.
3. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 11

7

Important:: The Powertrain Control Module (PCM) uses a single internal 5.0 volt power supply to power all the engine control components. If one component shorts its 5.0 volt reference circuit to ground or battery voltage, the other 5.0 volt reference circuits will also have a low or high voltage.

1. Test the 5.0 volt reference circuits for a short to B+.
2. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 8

8

1. Inspect the TP sensor connector for a poor connection at the TP sensor.
2. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 10

9

1. Turn OFF the ignition.
2. Test for an open in the TP sensor ground circuit.
3. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 11

10 | Replace the TP sensor. Refer to the Throttle Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 13 | --

11

1. Inspect for poor connections at the PCM connectors.
2. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 12

12 | Important:: The replacement PCM must be programmed and the Crankshaft Position Variation procedure must be performed. Refer to Powertrain Control Module Replacement/Programming and Crankshaft Position System Variation Learn . Replace the PCM. Did you complete the replacement? | -- | Go to Step 13 | --

13

1. Use a scan tool to clear the DTCs.
2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK